This invention relates to a resin composition and a laminate produced therefrom particularly suitable for malti-layer printed circuit boards excellent in heat resistance and high-frequency electrical properties.
Laminates made from phenol resins, epoxy resins and polyimide resins have mainly been used as laminating materials for multi-layer printed circuit boards. With recent progress for high speed treatment of large scale computers, printed circuit boards excellent in high-frequency electrical properties have been demanded in order to improve the signal transmitting rate. Particularly, in order to shorten the transmission delayed time and to thin the thickness of circuit boards, printed circuit boards having a low dielectric constant are disclosed (e.g. Proc. Int. Printed Circuits Cont., 1979, P. 179). As laminating materials for printed circuit boards having such excellent high-frequency electrical properties, there have been developed polytetrafluoroethylene laminates, butadiene resin laminates, and the like.
But in the case of polytetrafluoroethylene laminates, since the resin composition is a thermoplastic resin and very large in thermal expansion coefficient at high temperatures, there arises a problem in dimensional stability. Further, since the melting point of polytetrafluoroethylene in very high and there is no suitable solvent for preparing a vernish thereof, there is generally employed a laminating process by melt contact bonding with heating. Therefore, there are many difficulties in processability and moldability compared with conventional producing methods. A great change in the producing process is thus demanded.
On the other hand, in the case of butadiene resin laminates, since there can be obtained no solid prepreg at near room temperature in the production of prepreg when a low molecular weight polybutadiene is used, processability in winding up, laminating, and the like is worsened remarkably due to sticking properties of the prepreg. In order to solve such a problem, there is used a high molecular weight polybutadiene which is solid at near room temperature. But there arises another problem in that there can be obtained almost no fluidity at the time of molding with heating, that is, no fluidity can be obtained. Therefore, it is proposed to use two kinds of polybutadienes having different molecular weights mentioned above (Japanese Patent Examined Publication No. 21926/83). In such a case, the above-mentioned problem can be solved to some extent, but the problem of sticking properties at the time of prepreg production still remains unsolved.
It is also proposed to use a cyclized polybutadiene in place of the high molecular weight polybutadiene (Japanese Patent Examined Publication No. 57448/83), but the problem of insufficiency in mechanical strength and heat resistance, which problem is common to butadiene resin laminates, still remains unsolved.